Process of etching glass or the like



, Patented Oct. 13, 1925.

UNITED STATES.

PATENT OFFICE CLABKE 0., MINTER, OF NEW YORK, N. Y.

PROCESS OF 'ETCHING GLASS OR THE LIKE.

No Drawing. Application filedliay' 27:,- 1921, Serial No. 473,010.Renewed March 2, 1925.

To all'whiom it may concern:

Be it known that I, CLARKE C. MINTER, a citizen of the United States,residing at New York, in the wunty of New York and State of New York,have invented a certain new and useful Process ofEtching Glass or thelike, of which the following is a specification.

My invention relates to the etching of glass or the like, andparticularly to the etching of comparatively large portions of thesurfaces of articles an objects made of glass or the like, suchfor-example, as window glass, electric light bulbs, lamp shades,

lig t transmitted therethrough, and chinaware and porcelain articles toproduce or namental surface effects.

' As is well known, the agent most frequently used in the etching ofglass is hydrofluoric acid, a comparatively expensive agent and oneinthe use of which extreme care and precaution are necessary to beobserved to avoid injury to the o erator. The care and precautionrequire further increase the cost of the etching operation, the processwhen carried on commercially and to any substantial extent usually beingperformed in a specially-prepared chamber.

I Etching has also heretofore been done by the forcible projection ofsand or like abrading material against the surface to be etched, andthis process has the advantage over etching by hydrofluoric acid in thecheapness of the material used and the safety attending its use, but hasthe disadvantage that special apparatus andmachinery are required toproduce the blast of the abrading material.

My invention-has, among its objects, to

provide a process of etching eliminating the disadvantages of thecustomary processes heretofore mentioned, by the use of an etching agentor material of comparatively little 1produce ornamental effects ordiffusion of ditions of temperature of the glass or like obj eot to beetched and of the etching agent, a normal or an acid carbonate of analkali metal may be used as an effective etching agent.

I preferably employ sodium carbonate although I have also 'found amixture of sodium and potassium carbonate an effective agent, theaddition of .the'potassium salt-although having the disadvantage ofsomewhat-increasing the cost over the use of. the sodium saltalone-having the advantage of permitting a lower temperature at whichthe etching is effective. The cominercial, as distinguished from thechemi cally pure salts mentioned, may be used.

The range of temperatures, so far as the heating of the carbonate isconcerned, should include the fusion .point of the ,salt, and the heatneed not extend appreciably above that point.

The process of etching can be performed either at some stage during themanufacture of the glass or other like object when the heat thenbeingutilized in such manufacture can be utilized for this process reheatingthe object after its manufacture, and in the later instance, thetemperature need not be so high as to distort the object.

I have found that heating the object to be etched to approximately whatis familiarly known in the arts as a dull red heat of glass is apreferable degree of heat, although not an essential degree as the heatmay be varied above that temperature or below the same, the. etchingbeing possible at as low a temperature of the glass as approximately 300centigrade.

My invention may be carried out by any of the following illustrativeprocesses:

1'. The glass or like object to be etched is or by heated in an openflame, into which the desired carbonate, for example sodium carbonate infinely divided particles or powder form, is injected at some point belowthe glass object.

Any suit-able apparatus may be used for injecting the sodium carbonateinto the flame, such for example as an apparatus providing an air orother fluid pressure for blowing solid material in finely ividedparticles. I have found an ordinary bottle of appropriate size partlyfilled with the powdered salt and with a tube extending below thesurface of the salt within the bottle, and terminating outwardly in anozzle, and

the bottle provided with a collapsible bulb for the creation of an airpressure upon the salt, sufficient for the purpose.

The sodium carbonate thus injected into the flame is itself heated b theflame to the required temperature an quickly carried upwardly intocontact with the heated surface of the glass, and the particles of thesalt attack the glass wherever they come into contact therewith.

In this case, it is to be observed that a single heating medium isutilized to heat boththe glass to be etched and the etching agent.

The etching action apparently involves a reaction between the sodiumcarbonate and the silica of the glass. with the production of a solublesilicate, sodium silicate, which is removed by washing the glass withwater after the same has been cooled, and carbon dioxide which escapesas a gas. Other reactions may possibly be involved, but in any event,the surface of the glass or like article is pitted and roughened and thedesired effect produced.

The powdered salt is applied in the manner stated to the surface of thearticle after its manufacture, in which case its temperature is raisedto the required or desired degree, or duringsome stage of itsmanufacture when it is at the suitable temperature,

as, for example, between the blowing of theglass and the finishing ofthe article, or during the annealing of the same. The simplicity of theprocess renders it particularly applicable to the etching of the articleduring its process of manufacture, as indicated, and in the applicationof the process on a commercial scale, the apparatus for blowing thepowdered etching agent upon the surface of the article may. be locatedin the line of travel of the article through the various stages of itsmanufacture.

2. A melt of the desired carbonate or mix- .ture of carbonates, forexample, sodium car- Letters Patent is comprising heating the glass orthe like to be etched, directing sodium carbonate in finely dividedparticles into contactv with the surface to be etched, cooling thearticle thus heated and washing its said surface.

4. The process of etching glass or the like comprising heating the glassor the like to be etched, heating an alkali salt of carbonic acid toatleast the fusion of said salt, and causing contact of said fused saltwith the surface of said glass or the like to be etched.

5. The process of etching glass or the like comprising heating the glassor the like to be etched, heating an alkali salt of carbonic acid to atleast the fusion of said salt, causing contact of said fused salt withthe surface of said glass or the like to be etched,

thereafter cooling said article and washing its said surface.

6. The process of etchingglass or the like 7 i comprising heating theglass or the like to a vtemperature approximately 300 degrees centigradeor above, heating an alkali salt of carbonic acid to at least the fusionof said salt, andcausing contact of said fused salt with the surface ofsaid glass or the like to be etched.

7. The process of etching glass or the like comprising heating the glassor the like to a temperature approximately 300 degrees centigrade orabove, heating an alkali salt of carbonic acid to at least the fusion ofsaid salt, causing contact of said fused salt with the surface'of saidglass or the like to be etched, cooling the article thus treated andwashing the said surface.

8. The process of etching glass or the like comprising heating the glassor the like to a temperature approximately 300 degrees centigrade orabove, heating sodium carbonate to at least the fusion point of saidsalt, causing contact of said fused salt with the surface of said glassor the like .to be etched, coolin the article thus treated and washingits sald surface. g

9. The process of etching glass or the like comprising heating the glassor the like 'in' an open flame, and directing an alkali salt .ofcarbonic acid in finel divided particles into said flame into posltionto be carried upwardly thereby into contact with the surface to beetched.

10. The process of etching glass or the.

like comprising heating the glass or the like in an open flame,'anddirecting sodium carbonate in finely divided particles into said.

May, 1921. I

' CLARKE O. MINTER.

